Daily Challenge #9 - What's Your Number?

Can I have your number?

Write a function that accepts an array of 10 integers (between 0 and 9), that returns a string of those numbers in the form of a phone number.

The returned format must be correct in order to complete this challenge.
Don't forget the space after the closing parentheses!

Today's challenge comes from user xDranik on Codewars

Thank you to CodeWars, who has licensed redistribution of this challenge under the 2-Clause BSD License!

Want to propose a challenge for a future post? Email [e-mail] with your suggestions!

Comments

[official_dulin]

Go:

import (
  "fmt"
  "strconv"
  "strings"
)

func CreatePhoneNumber(numbers [10]uint) string {
  strs := []string{}
  for _, n := range numbers {
    strs = append(strs, strconv.FormatUint(uint64(n), 10))
  }
  a := strings.Join(strs[:3], "")
  b := strings.Join(strs[3:6], "")
  c := strings.Join(strs[6:], "")
  return fmt.Sprintf("(%s) %s-%s", a, b, c)
}

[peter279k]

Here is the simple solution with PHP:

function createPhoneNumber($numbersArray) {
    $format = "(%s%s%s) %s%s%s-%s%s%s%s";

    return sprintf(
      $format,
      $numbersArray[0], $numbersArray[1], $numbersArray[2], $numbersArray[3],
      $numbersArray[4], $numbersArray[5], $numbersArray[6], $numbersArray[7],
      $numbersArray[8], $numbersArray[9]
    );
}

[Rohit Prasad]

Python

var = input("Enter 10 integers: ")
var = list(var)

if len(var) != 10:
        print("Invalid Entry")
else:
        print('(',var[0],var[1],var[2],') ',var[3],var[4],var[5],'-',var[6],var[7],var[8],var[9], sep='')

anyone's skin crawling?

[Siddharth Venkatesan]

Ruby

def phone_number(nums)
  puts "(#{nums[0..2].join("")}) #{nums[3..5].join("")}-#{nums[6..-1].join("")}"
end

puts phone_number([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]) #[phone]

[margo1993]

package utils

import (
    "errors"
    "fmt"
    "strconv"
)

func FormatPhoneNumber(phoneNumberArray []int) (string, error) {

    if len(phoneNumberArray) != 10 {
        return "", errors.New("Array length must be 10")
    }

    return fmt.Sprintf("(%s) %s-%s", intArrayToString(phoneNumberArray[:3]), intArrayToString(phoneNumberArray[3:6]), intArrayToString(phoneNumberArray[6:])), nil
}

func intArrayToString(intArray []int) string {
    number := ""

    for _, num := range intArray {
        number += strconv.Itoa(num)
    }

    return number
}

[Ilyes Chouia]

Better late than never ;p

Here's my attempt in PHP

function formPhoneNumber(array $integers): string
{

    if(count($integers) != 10) {
        throw new Exception('Please provide a valid array!');
    }

    $phone = "(";
    foreach($integers as $index => $number){
       if($number < 10 && $number >= 0){
            $phone .= $number;
            if($index == 2){
                $phone .= ") ";
            }elseif($index == 5){
                $phone .= "-";
            }
       }else{
            throw new Exception("One of the numbers is invalid!");
       }
    }
    return $phone;

}
echo formPhoneNumber([4, 5, 5, 4, 5, 1, 7, 8, 9, 0]);

[Kevin Sullivan]

codesandbox.io/embed/daily-challen...

const iterative = (input: number[], schema: string = "(###) ###-####") => {
  let result = schema;
  input.forEach(number => (result = result.replace("#", String(number))));

  return result;
};

const recursive = (
  input: number[],
  schema: string = "(###) ###-####",
  result: string = schema
): string => {
  const [head, ...rest] = input;
  if (head === undefined) return result;

  return recursive(rest, schema, result.replace("#", String(head)`));
};

export const createPhoneNumber = {
  iterative,
  recursive
};

[Craig McIlwrath]

Haskell (US formatting):

formatNumber :: [Int] -> Maybe String
formatNumber xs
  | length xs /= 10 = Nothing
  | not $ and $ (map (<10) xs) ++ (map (>=0) xs) = Nothing 
  | otherwise = Just $ "(" ++ (showSlice 0 3 xs) ++ ") " ++ (showSlice 3 3 xs) ++ "-" ++ (showSlice 6 4 xs) 
  where showSlice from len = concat . map show . take len . drop from

[jmc]

Clojure:

(defn format-number [digits]
  (apply format "(%s%s%s) %s%s%s-%s%s%s%s" digits))

[Steve Moon]

Erlang: (in the REPL)

Num = [8,0,0,5,5,5,1,2,1,2].
io:format("(~B~B~B) ~B~B~B-~B~B~B~B~n", Num).
[phone]
ok

Or you can use io_lib:format and assign the result to a variable instead.

Checking for valid input is fairly trivial, but the Erlang convention is to assume that something this far into the system is okay, and correct for the error by dying and letting the supervisor deal with it.

[Kasper Meyer]

Ruby solution

require "minitest/autorun"

class PhoneNumberFormatter
  def initialize digits
    @digits = digits
  end

  def format
    "(#{area_code}) #{central_office_code}-#{line_number}"
  end

  private

    def area_code
      @digits[0..2].join
    end

    def central_office_code
      @digits[3..5].join
    end

    def line_number
      @digits[6..9].join
    end
end

class PhoneNumberFormatterTest < MiniTest::Test
  def test_formatted_phone_number
    output = PhoneNumberFormatter.new([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]).format

    assert_equal "[phone]", output
  end
end

[Franco Traversaro]

No PHP solutions yet? Here I come!

<?php

function phoneFormat(array $numbers): string
{
    if (10 !== count($numbers)) {
        throw new \RuntimeException("Wrong input");
    }
    array_unshift($numbers, '(%d%d%d) %d%d%d-%d%d%d%d');

    return call_user_func_array('sprintf', $numbers);
}

assert('[phone]' === phoneFormat([1, 2, 3, 4, 5, 6, 7, 8, 9, 0]), "Function not functioning :-/");

But please edit the OP to explain what format do you want, not everybody comes from USA!

EDIT: added length validation

[Corey Alexander]

My Rust Solution and test cases!

I felt this one was a little easier than some of the previous days, but nothing wrong with that!

#[derive(Debug, PartialEq)]
pub enum Error {
    InvalidLength,
    NotSingleDigitInput,
}

pub fn format_phone_numer(numbers: &[u32]) -> Result<String, Error> {
    if numbers.len() != 10 {
        Err(Error::InvalidLength)
    } else if numbers.iter().any(|x| *x > 9) {
        Err(Error::NotSingleDigitInput)
    } else {
        Ok(format!(
            "({}{}{}) {}{}{}-{}{}{}{}",
            numbers[0],
            numbers[1],
            numbers[2],
            numbers[3],
            numbers[4],
            numbers[5],
            numbers[6],
            numbers[7],
            numbers[8],
            numbers[9],
        ))
    }
}

#[cfg(test)]
mod tests {
    use crate::*;

    #[test]
    fn it_for_a_valid_phone_number() {
        assert_eq!(
            format_phone_numer(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 0]),
            Ok("[phone]".to_string())
        );
        assert_eq!(
            format_phone_numer(&[3, 2, 1, 5, 5, 5, 3, 1, 6, 3]),
            Ok("[phone]".to_string())
        );
    }

    #[test]
    fn it_errors_invalid_length_phone_number() {
        assert_eq!(
            format_phone_numer(&[1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 5, 6, 3]),
            Err(Error::InvalidLength)
        );
        assert_eq!(
            format_phone_numer(&[1, 2, 3, 4, 5, 6, 7,]),
            Err(Error::InvalidLength)
        );
    }

    #[test]
    fn it_errors_for_non_single_digit_numbers() {
        assert_eq!(
            format_phone_numer(&[10, 2, 3, 4, 5, 6, 7, 8, 9, 0]),
            Err(Error::NotSingleDigitInput)
        );
    }
}

[E. Choroba]

#! /usr/bin/perl
use warnings;
use strict;

sub phone_num {
    local $" = "";
    "(@_[0 .. 2]) @_[3..5]-@_[6..9]"
}

use Test::More tests => 1;
is phone_num(0 .. 9), '[phone]';

The special variable $" is used to separate arrays interpolated in double quotes. By default, it contains a space, but we need the numbers to be adjacent, so we set it locally (i.e. in a dynamic scope) to an empty string.

Another possible short solution is

sub phone_num {
    "[phone]" =~ s/(\d)/$_[$1]/gr
}

The substitution replaces each digit in the template string with the corresponding element of the @_ array which keeps the list of the subroutine arguments. /g means "global", it's needed to replace all the digits, not just the first one. The /r means "return" - normally, a substitution changes the bound left-hand side value, but with /r, it just returns the value.

[Yozen Hernandez]

Nice, basically what I got. sprintf works as well.

#!/usr/bin/env perl

use strict;
use warnings;

sub createPhoneNumber {
    sprintf "(%s%s%s) %s%s%s-%s%s%s%s", @_;
    # local $" = "";
    # "(@_[0..2]) @_[3..5]-@_[6..9]";
}

print createPhoneNumber(1, 2, 3, 4, 5, 6, 7, 8, 9, 0) . "\n";

The regex solution was pretty interesting. Thanks for the explanation!

[Fernando B 🚀]

I am not a big fan of code challenges in this format. For one people can see other answers. That can skew your thinking before even attempting the challenge. Secondly I think you should submit your own answers on codewars, and then link it here. Only people that has passed the challenge would be able to see it.

@ben definitely need a spoiler tag.